1. Field of the Invention
This invention generally relates to discharge lamps and has particular reference to an improved fluorescent lamp of compact size and high brightness that has a partitioned envelope and is suitable for use in residential and commercial lighting fixtures.
2. Description of the Prior Art
Electric discharge lamps having envelopes which are internally partitioned to provide one or more elongated discharge paths are generally well known in the art. U.S. Pat. No. 2,121,333 to Barclay discloses a single-ended type lamp of such construction wherein glass panels joined to the glass envelope serve as the partition means. Another fluorescent lamp of this general type is disclosed in U.S. Pat. No. 3,024,383 to Doering and employs a thin sheet of glass or suitable ceramic as the partition means which divides the interior of the envelope into either two or four sectors. A double-ended fluorescent lamp having a longitudinal partition that extends along the axis of the envelope between two pairs of oppositely-disposed electrodes to provide a dual-arc device is disclosed in U.S. Pat. No. 3,084,271 to C. E. Swanson.
Discharge lamps having envelopes with partition means or a filler or core member that prevents the arc passing between the electrodes along the axis of the envelope are also generally well known in the art. For example, in U.S. Pat. No. 1,963,962 to Barclay the tubular envelope of a discharge lamp is partitioned in such a manner that a plurality of arc channels disposed around a central bore or channel are provided. U.S. Pat. No. 2,133,205 to McCauley discloses a tubular double-ended discharge lamp that has a channelled core or filler member which forces the arc to follow different paths and produce a changing luminous effect. Various types of fluorescent lamps having envelopes that are so constructed that the discharge is prevented from passing along the center of the envelope (or is made to follow a path around an inner envelope) component are disclosed in U.S. Pat. Nos. 3,521,120 (Anderson); 3,953,761 (LoGiudice, FIGS. 6-8 embodiments); and 4,095,135 (Yamazaki et al). Fluorescent lamps having bulbs which force the arc to follow a helical path around the bulb axis are disclosed in U.S. Pat. Nos. 3,899,712 to Witting and 3,903,447 to Young et al.